• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2002.02a
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• pp.210-216
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• 2002

본 연구는 오이 수확기 개발을 위해 메니퓰레이터를 설계 제작하였다. 실험에 사용한 3축 메니퓰레이터는 견고성, 내구성, 모멘트를 줄이기 위해 모터 및 감속기 등이 하중이 실리지 않는 곳에 장착하였다. 주요 연구 결과를 요약하면 다음과 같다. 1) 3차원 공간상의 좌표에 대하여 메니퓰레이터의 10회 반복 위치 오차는 Z축에 관계없이 0.1mm 내외로 정확하게 작동하는 것으로 나타났다. 2) 실내 실험에서 25개의 오이에 대한 실험 결과 22개의 절단하여 92%의 성공률을 보였으나, 원인은 오이가 기형과이며, 수확한 후 시간이 경과하여 오이 과병의 물성이 변한 것으로 판단된다. 3) 실내 실험에서 오이 과병을 절단하지 못한 경우에도 메니퓰레이터는 오이에 0.1m 내외로 엔드이펙터을 접근시켰다. 4) 50개의 오이에 대하여 현장 실험을 한 결과 42개, 84%의 절단율을 보였다. 오차가 16% 발생한 것은 수확적기가 지나서 오이의 과병이 짧고 뭉툭해서 나타난 것으로 판단된다.

• 기계와재료
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• v.21 no.3
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• pp.52-59
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• 2009

테이퍼롤러 베어링의 축방향 과다 예압에 의한 수명 단축 효과를 실험적으로 검증하고 그 결과에 의한 베어링의 수명 분포를 분석하여, 기존의 $L_{10}$ 수명식에 비하여 현장 작동 조건에 따른 실질적인 수명을 산출할 수 있는 축방향과 반경방향을 고려한 수명식을 도출하고 이를 프로그램화 하여 설계 및 생산 현장에서 용이하게 활용할 수 있도록 하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.359-364
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• 2007

Spray characteristics of the APU gas turbine engine were investigated. In order to understand blow out phenomena of the APU engine, we performed fuel spray test. In the test, four operating conditions such as sea level idle, sea level max power, 20,000 feet idle, 20,000 feet max power were used as spray experimental conditions. PDPA(phase Doppler Particle Analyzer) was used for measuring the particle diameter and velocity. Also spray visualization was performed by using ND-YAG sheet laser beam. From the test result, in the case of 20,000 feet idle condition, SMD is about 100 ${\mu}m$ and maximum particle velocity is about 10 m/s. For the flame stability, spray quality should be improved at 20,000 feet idle condition.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.9
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• pp.815-821
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• 2013

The efficiency and lifetime of a polymer electrolyte membrane fuel cell (PEMFC) system is critically affected by the humidity of the incoming gas, which should be maintained properly under normal operating conditions. Typically, the incoming gas of a fuel cell is humidified by an external humidifier, but few studies have reported on the device characteristics. In this study, a laboratory-scale planar membrane humidifier is designed to investigate the characteristics of water transport through a hydrophilic membrane. The planar membrane humidifier is immersed in a constant temperature bath to isolate the humidifier from the effect of temperature variations. The mass transfer capability of the hydrophilic membrane is first examined under isothermal conditions. Then, the mass transfer capability is investigated under various conditions. The results show that water transport in the hydrophilic membrane is significantly affected by the flow rate, operating temperature, operating pressure, and flow arrangement.

• Journal of the Korean Institute of Gas
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• v.16 no.6
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• pp.73-79
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• 2012

Currently, all domestic CNG vehicles have manual cylinder valves installed. These are inconvenient for drivers in case of a gas leak accident, because drivers have to stop the vehicle operation and manually close the valve. It makes difficult condition for drivers to quickly and properly respond to such accidents. In advanced European countries, they require Automatic cylinder valve installation, which has a structure where the valve is automatically shut off when the driver turns off the ignition in case of a gas leak. If this electric valve system is introduced in Korea, the safety of CNG buses will be improved with better functionalities. In this paper, in order to solve the structural problem of difficulty for a driver to identify the operational status of individual Automatic cylinder valves, an approach was made regarding temperature increase with pressure increase during CNG filling. it was estimated that the temperature increased approximately more than $30^{\circ}C$ due to pressure difference during the filling. Therefore, it was concluded from the experimental data that the valve of the container whose temperature did not increase did not operate, resulting in filling failure.

• Composites Research
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• v.20 no.3
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• pp.50-54
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• 2007

The Ionic Polymer Metal Composite (IPMC), an electro-active polymer, has many advantages including bending actuation, low weight, low power consumption, and flexibility. These advantages coincide with the requirements of a bio-related application. Thus, IPMC is promising materials for bio-mimetic actuator and sensor applications. Before applying IPMC to actual application, basic mechanical properties of IPMC should be studied in order to utilize IPMC for practical uses. Therefore, IPMCs are fabricated to investigate the mechanical characteristics. Nafion is used as a base ionic polymer. Mason samples cast with various thicknesses are used to test the thickness effects of IPMC. Subsequently, IPMC is fabricated using the chemical reduction method. The deformation, blocking force and frequency response of the IPMC actuator are important properties. In this present study, the performances of the IPMC actuators, including the deformation, blocking force and natural frequency, are then obtained according to only the input voltage and IPMC dimensions. Finally, the empirical performance model and the equivalent stiffness model of the IPMC actuator are established using experiments results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.120-122
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• 2014

선박의 조타기 작동 신호를 AIS를 통하여 전달함으로써 상대선박의 변침의도를 신속히 파악하여 충돌위험을 피할 수 있는 선회조기감지시스템을 구현하고 실선실험을 통하여 그 실효성을 검증하였다. 또한, 실선실험을 통해 선박의 타각정보가 AIS를 통해 송 수신이 가능하다는 것을 확인하였으며, ECDIS에 표시된 타각정보는 주변선박의 충돌회피에 크게 기여할 것으로 판단된다. 선회조기감지시스템은 선박의 안전운항을 위한 정보 제공의 필요성, 선박 통항량 증가 및 고속화 등으로 인한 위험성 증대로 VTS관제의 역할이 더욱 중요시 되고 있는 상황에서 선박의 조타각이 표시된 해당 시스템을 활용할 경우 변침상황을 보다 신속히 파악할 수 있으므로 관제가 보다 쉬워질 것으로 예상된다. 또한, 선박의 침몰이나 VDR의 소실로 인한 해양사고 분석의 어려움도 AIS를 통한 조타신호가 저장된 해양안전종합정보시스템(GICOMS)의 분석을 통해 다소 해소될 것으로 판단된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.7
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• pp.635-640
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• 2015

In this paper, we report a non-explosive separation device for a small satellite which utilize a shape memory alloy actuator. Based on previous research, we try to increase the reliability of the proposed device by changing some components. It enables the proposed device to activate under high preload. Also, we confirm it generates low shock which is main advantage of non-explosive separation device. Finally, vibration test which mimics launching environment and thermal vacuum test which mimics space environment are carried out respectively. After each environment test, we confirm the proposed device is successfully activated. Conclusively, we develop a non-explosive separation device which can activate with low shock under high preload after shock and environment tests(vibration and thermal vacuum tests).

• Fire Science and Engineering
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• v.31 no.1
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• pp.50-57
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• 2017

The present article discusses the response characteristics of smoke detector chamber due to dust and wind velocity. Although situations have improved in terms of early sensing of fires as the smoke detectors are applied indoors, studies tend to place insufficient focus on the side effects and malfunction that can be caused by diversified life dust produced indoors and environmental requirements, etc. Therefore, in the present study, 4 types of photoelectric smoke detectors with different forms and structures of smoke chamber were selected as the experimental objects, and dust test was conducted with fly ash, talcum powder and fiber dust as experiment samples to study indoor applicability of the smoke detectors in terms of their response to diversified dust and wind velocity. Also, to observe response characteristics due to pollution level inside the smoke chamber, wind velocity for dust test were set additionally at 0.25 m/s, 0.5 m/s, and 1.0 m/s. Based to the experimental results, fly ash, talcum powder, and fiber dust (black hair powder) were found to be suitable at the dust test reference wind velocity conditions of 0.25 m/s for both operation test and non-operation test after dust application. On the other hand, under the harsh wind velocity conditions of 0.5 m/s and 1.0 m/s, malfunction of unwanted alarm was observed in non-operation tests in the case of fly ash and talcum powder, and non-operation was confirmed to occur in the case of fiber dust as the alarm failed to operate normally in operation tests.

• Composites Research
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• v.18 no.5
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• pp.34-39
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• 2005

The relationship between strain and applied potential was derived for composite actuators consisting of single-wall carbon nanotubes (SWNTs) and conductive polymers (CPs). During deriving the relationship, an electrochemical ionic approach is utilized to formulate the electromechanical actuation of the composite film actuator. This relationship can give us a direct understanding of the actuation of a nanoactuator. The results show that the well-aligned SWNTs composite actuator can give good actuation responses and high actuating forces available. The actuation is found to be affected by both SWNTs and CPs components and the actuation of SWNTs component has two kinds of influences on that of the CPs component: reinforcement at the positive voltage and abatement at the negative voltage. Optimizations of SWNTs-CPs composite actuator may be achieved by using well-aligned nanotubes as well as choosing suitable electrolyte and input voltage range.